Unproffessional banking

I placed myself under debt review in Covid. I worked hard to pay it off a soon as possible. I am now paid up but now FNB has finance errors on their side. I asked for my last settlement letter. They let me know that I overpaid. So FNB refunded me R1 357 and was suppose to settle the last account. But then I still got messages that I am in arrears of R5 738. So after 3 MONTHS of asking why it has not been settled I keep sending emails and ask on secure chat what is going on. A week ago they said that they will settle the R5 738 and they will sort it out. After a week they did not only not settle the account AGAIN... now my last account that showed R5 738 in arrears a week ago...now it shows R12 838 in arrears, for no reason whatsoever. But wait, it gets more unprofessional from FNB. They refunded me AGAIN for R1 357...I do not know why...just to debit it from my account 2 days later. Obviously realizing their mistake. I need answers. Why has this not been settled? Why did my arrears increase in 5 days by R7 100. Why has no one contacted me to explain. How can I trust a bank that does not know what is happening in their own departments and messing up finances. This needs to be sorted out NOW. Me the customer cannot email and phone every day to try and sort this out.